PHILADELPHIA — Don't stay at home this November, former President Jimmy Carter said Tuesday night.

This "will be a very important election, one that will define for a generation who we are as a nation and as a people," the 39th president said in a video address at the Democratic National Convention. "At a moment when it's become more important than ever to lift people up, … we see a Republican candidate who seems to violate some of the most important moral and ethical principles on which our nation was founded."

"We can, and must, do better," he said.

Before Carter's address was delivered, Hillary Clinton officially became the Democratic nominee, making her the first woman in a major U.S. political party to win the nomination.

On the road to her historic nomination, she overcame the fierce challenge by Sen. Bernie Sanders of Vermont during the primaries.

"We Americans have a clear choice before us. I feel proud that the two Democratic candidates, who competed through a long primary season, … comported themselves with dignity, talked about issues that matter, and presented a vision for our nation," Carter said. "I thank Senator Sanders for energizing and bringing so many young people into the electoral process. To all of you young Americans, I say: Stay engaged, stay involved and be sure to vote this November."

The 91-year-old Carter revealed last August that he had cancer and that it had spread to his brain. However, the drug pembrolizumab helped keep it from spreading further. In fact, the drug was so effective that researchers stopped a study on the drug, saying it worked so well they wanted to offer it to everyone in their trial.

Last November, he said he was doing well on his treatments, with no signs of more spreading.

In introducing Carter, his grandson Jason said Tuesday that "the cancer is gone."